Introduction To TCP/IP Model ( DOD Model)-The Application/Process Layer Protocols
As we know the Application , presentation and session layer of OSI in together corresponds to the Process or Application layer of TCP/IP model. The various protocols that are associated with Process layer are DNS,SNMP,telnet ,ftp,tftp,nfs etc and the list goes . I am going to explain a few . You may need to have them running on your system when you later advance in your expertise skills in networking as they are useful.
1.)FTP-FILE Transfer Protocol-The ftp is a widely used protocol used to copy files from one network location to another network locations. It uses a client server model and uses 2 channels one for data and one for control. The port number used are 21 and 20 . I will come to concepts of port numbers later.
The ftp transmission may or may not work without a username or password . If username and password are not set then we can login via anonymous account .The data via ftp is not secure to add security we use SCP i.e. call stream copy over SSH. If you want to try FTP at home you can download filezilla server and filezilla client
2.)TFTP-Trivial File Transfer Protocol-You can say that TFTP is a protocol which was produced after keeping FTP on diet for a year. Hahah It’s the low stripped down version of FTP . It is so small that it can be easily be put on small rom chips which are few kb in size. This is used to boot computer and routers which do not have enough memory for Operating system.
Almost all the features of FTP are missing in TFTP.It can only read or write directories but cannot list directories. It can also mail from a remote server or vice versa. And also there is no user authentication
TFTP is designed to be small and easy to implement, therefore, lacks most of the features of a regular FTP. TFTP only reads and writes files (or mail) from/to a remote server. It cannot list directories, and currently has no provisions for user authentication. It uses port 69.TFTPD32 is a nice TFTP server.
3.)Telnet-(Terminal Network)-It is a network protocol which help you to access remote devices over lan or over internet. The connection is bidirectional textual over command line .The port used is 23 . The data which travels is unsecure and can be seen by anyone on the internet so SSH was introduced which incorporates encryption too. If I need to configure in my LAN environment I will use a TERMINAL emulation software like(HyperTerminal or Tera Term) they help you connect with your device via telnet.
4.)DNS(Domain Name Service)-Consider all person in this world recognized by their cell numbers so what will happen. Hey have you seen 7863142 today ?? Whos he …
Hey 2671242 turned CCIE today . Oh my God thank god we have names. This is same for internet addresses if you want to reach google.com you just type google.com in the browser not their ip address(which can be xxx.xxx.xxx.xxx) or anything . The service which maps the domain names to their Ip address is called DNS . Its just like an address book or contact book in your phone when you want to call your friend you just have to search his name from the contacts and press dial It will automatically call your friend .